Propeller Assembly

ABSTRACT

Disclosed herein is an inventive dual propeller assembly that can be manually or automatively assembled and includes a leading propeller, a torsion bushing, a thrust washer, a drive sleeve, and a trailing propeller. The propellers were coupled with an alignment system that did not require welding of the two propellers. The leading propeller includes a cylindrical hub and a plurality of blades that extend from an outer surface of the cylindrical hub. The trailing propeller includes a first cylindrical hub having a plurality of grooves, a second cylindrical hub having a cylindrical mount ring, and a conical profile formed between the first cylindrical hub and the second cylindrical hub. The outer surface of the first cylindrical hub is designed to mate with the inner surface of the cylindrical hub of the leading propeller. The trailing propeller is secured and aligned coaxially with the leading propeller. The trailing propeller can be effectively and consistently used with existing propellers.

CROSS REFERENCE TO RELATED APPLICATION(S)

This is a non-provisional patent application based on co-pending U.S.Provisional Patent Application Ser. No. 62/354,411 (Attorney Docket No.MK-16-1) previously titled “Propeller Assembly”, filed on Jun. 24, 2016,the priority of which is hereby claimed and the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND Field of the Invention

The present invention relates to a propulsion system for watercraft.More particularly, the present invention relates to an auxiliarypropeller used in an axial arrangement with a standard propeller in thepropulsion system.

Description of the Related Art

Propulsion systems are used to generate thrust to move a watercraft(also referred to herein as boat and defined as any vessel capable ofmoving through a water way with use of an engine and propeller). acrossor through water. Most of the watercrafts are propelled by mechanicalsystems that include an electric motor or an engine which powers apropeller. Boats often have one or two propellers (also called props)attached thereto for speed through the water. The propeller is generallysecured to the rear portion of the electric or gas engine. To navigatethe watercraft, the propeller is rotated in either a clockwise orcounter-clockwise direction. Typically, once the boat is in shallowwater, it will have difficulties pulling out to the deeper end. A boator watercraft will displace water underneath its hull until the weightof the hull and the weight of the water displaced equal. This istypically called hole shot in boating terms since essentially a hole isformed under the boat. Sometimes the hole shot is also referred to asgetting skeg out of the sand, acceleration from a standing position, orgetting the boat from plane to acceleration. The hole shot is importantinformation for determining proper hull/power combination. The faster aboat is able to achieve plane, the less fuel is consumed.

If the boat engine is started and the boater begins to navigate throughthe waterway at a closed throttle, generally the boat remains in thehole, i.e., the hole simply moves with the boat. The hull remains low,sitting in the water hole that was formed by the displacement of theboats' hull. To get out of the hole, a boater needs to move the boatfast enough so that it can exceed the speed of the hole that is movingunder the boat and have enough power and torque to get the boat to climbthe hole in a decent amount of time. In boating, a good hole shot is theability to get up on plane (“getting out of the hole”) and up to speedquickly from a stopped position. A poor hole shot would often be causedby the motor laboring and taking a long time to get up to speed (oftenbecause not properly propped for the load, or the boat is underpowered).

As an example, a high powered boat may have excellent top speed, but apoor hole shot, i.e., as the boat begins to move, the boats' holecontinues to move and even perhaps increase in depth due to the changingangle of the boat. So when the boat begins to climb out of the holethere is less total hull sitting in the water, and the smaller hull,having the same weight will tend to settle deeper into the water. Butnow as the boat begins to move, the boat will gradually start climbingthe steep edge of the hole. As the boat climbs higher, the edge of thehole gets less steep—hence you see the bow of the boat begin to droplower. Finally as the boat is almost out of the hole, the boat will benear level and the boat will be moving fast enough to plane on top ofthe water, leaving the hole behind. Now, if you take the same highpowered boat with a much lower pitch and possibly larger diameterpropeller, the engine will be able to spin the larger diameter propellermore quickly, be able to more quickly accelerate the boat, and will morequickly climb out of the hole.

A lower pitched propeller, which may help in removing the boat from ahole shot, has the disadvantage of generally having a lower top speedmotor (defined herein as the engine and propeller). This is because thelower pitched propeller cannot navigate (or screw) itself though thewater, as easily as a higher pitched propeller.

The ability to get the boat on plane quickly is important for safety asmuch as any other reason. The quicker a boater can get the bow backdown, the sooner s/he can see what is in front of them and avoid anyunsafe situations, as well as keep themselves and other boat passengersdry.

Hole shot-related problems often occur during take-off of a boat, andmost often in shallow versus deep water. Existing motors having singlepropellers typically perform poorly in shallow water since they cannoteasily overcome the hole shot caused. To overcome the problems listedabove, boaters have experimented with using multiple motors on the boatfor increased speed, modifying the shape of the blades of the propeller(also called cupping), modifying the venting arrangement of the exhaustsaround the propeller to aerate the water surrounding it, or changing orenhancing the rotational speed of the propeller in existing motors.Other avenues considered for this problem were to modify the boatitself, such as in using trim tabs to keep the boat flat when coming outof a hole.

It is well known that a watercraft with dual propellers generates astronger thrust force than the thrust generated by those equipped with asingle propeller. Most known dual-propeller watercrafts require dualengines, each of which powers a corresponding propeller. Thus, having adual propeller system is impractical for small and inexpensivewatercrafts. There exists a need for an inexpensive, easy to produce,dual propeller system that uses a single engine to power the twopropellers, thus reducing the expense and weight of the watercraft andgenerating a strong thrust force.

Art located includes:

U.S. Pat. No. 2,672,115 to Warren discloses a propulsion device withdual propellers.U.S. Pat. No. 3,261,229 to Dallas et al. discloses a propulsion systemfor a boat.U.S. Pat. No. 3,470,961 to Halsmer discloses a clutch for a twin engineaircraft with two propellers that are mounted coaxially on a singleshaft.U.S. Pat. No. 3,922,997 to Jameson discloses a marine power transmissionsystem.U.S. Pat. No. 4,865,520 to Robert et al. discloses a marine propellerwith an addendum.U.S. Pat. No. 5,074,814 to Alan discloses a self-contained outboard twinpropeller adaptor.U.S. Pat. No. 5,494,466 to Stefan discloses transmission of dualpropellers driven by an inboard marine engine.U.S. Pat. No. 6,435,923 to Ferguson discloses a two-speed transmissionwith reverse gearing for watercraft.U.S. Pat. No. 6,899,576 to Reinhold et al. discloses a twin-propellerdrive for watercraft.U.S. Pat. No. 8,668,533 to Philip discloses a water jet-based propulsionsystem that utilizes more than one water jet outlet port to controlselective application of power to the water jets, using a splittergearbox, thereby improving the efficiency of the marine craft at low andhigh speeds.U.S. Pub. No. 2005/0064772 to Karel et al. discloses a dual propellerdrive for a ski boat.U.S. Pub. No. 2015/0047543 to Thomas discloses propulsion arrangementfor a marine vessel.DE 2427245 to Rudolf teaches a drive system for a power glider that hastwin propellers mounted on arms with belt drives that are foldable intothe fuselage.EP 1476352 to Graham discloses a marine counter-rotating shaft drivemechanism.WO 1993/000529 A1 to Richard discloses a power transmission for use inmarine inboards.

Most of the patents mentioned above disclose the use of propulsionsystems that run two propellers with a single engine. Chain and sprocketarrangements are used to transfer power from the drive shaft of theengine to twin propeller shafts driving twin propellers. The propellersare arranged axially. However, the problem with most of the prior artsystems is that the propellers wear out quickly and hole shotdiminishes. Typically, dual propellers, which are coaxially aligned anddriven in the same direction, are welded together. The welding of twopropellers is time-consuming and labor-intensive and often shrinks thebarrel of the propeller. This does not allow a smooth fit between thetwo propellers. This misalignment causes pulling and eventual burning ofthe propellers. The problem with welding is that the metals do notattach evenly, since the metal expands and shifts a little, resulting inthe components not fitting snugly. Over time, use and vibration, theweld may sustain itself, but the propeller burns out.

In light of the foregoing, there exists a need for an easy to prepare,inexpensive, mechanism and/or a propeller to enhance the thrust force ofa watercraft engine, improve the hole shot and maintain (or obtain) topspeed of the watercraft.

SUMMARY

Disclosed herein is an easy and inexpensive method to increase power toa boat motor. While the problem to be solved was avoiding hole shotissues for boats in shallow water, the present invention has numerousbenefits beyond the remedy for hole shot concerns. Further disclosed isan auxiliary propeller allowing the combining of two propellers in placeon any given engine. This is not suitable for counter-rotating systems,but otherwise useful or suitable for all single output shafts. Stillfurther disclosed is a unique coupling system to attach two propellerstogether without the need for a method of adhesively securing. Herein,adhesively securing is defined as welding, a chemical adhesive suitablefor metal or plastic, or screws to hold the propellers in place or thelike. Assembly of the dual propellers can be achieved manually orautomatively (or by machine). The dual propeller system increases thethrust, and power of the boat. A perfect alignment is formed when thetwo propellers are combined, minimizing or eliminating the problemscaused by welding or securing propellers with screws (problems such aspull of the metal, vibrations weakening the weld or attachment). Abarrel or coupling device having a crown (grooves) was developed whichfits securely in the interior section of the lead propeller, and allowsfor the combining of two propellers onto one engine. It was found thatthe present inventive device was able to move a boat out of shallowwater using about half the RPMS (rotations per minute) than wouldnormally be used. For exemplary purposes, most hulls require less than2500-3000 RPMS to get on plane in shallow water conditions (shallowwater defined herein as about 0″-12″ of water, or preferably anythingless than 6″) with this device; with existing propeller systems it wouldrequire wide open throttle to get out of the hole.

An object of the present invention is to provide a method to enhance thepower and thrust of an watercraft engine by combining two propellers;one becomes the trailing propeller that is secured and aligned coaxiallywith an existing or lead propeller. The trailing propeller includes afirst cylindrical hub (or barrel with grooves at its end, also referredto as a coupling system), a second cylindrical hub (accepting the barrelwith grooves), and a conical profile there between. The firstcylindrical hub or barrel includes a plurality of grooves on one endthat are described and shown herein as rectangular in shape. Whilerectangular is a preferred shape, other shapes such as semi-circular,square-like, round over, V-groove, etc. are acceptable provided thegroove fit into propeller. The shape allows the figure sliding over thelead propeller. The grooves are to be aligned with preferably 30°increments for timing purposes and are equidistant to each other. Thesecond cylindrical hub includes a cylindrical mount ring that holds adrive sleeve. The cylindrical mount ring is attached to the secondcylindrical hub or spline by using a set of radial mount ring flanges.The conical profile formed between the first cylindrical hub or barrel,and the second cylindrical hub allows smooth alignment of the trailingpropeller with most if not all of current or existing propellers. Thefirst cylindrical hub having the barrel with grooves is inserted in ahub (or interior portion) of the existing propeller. The outer diameterof the barrel is selected based on the inner diameter of the hub of theexisting propeller. The trailing propeller can be effectively andconsistently used with propellers made by any existing manufacturer.

The present invention comprises a barrel having grooves on one end, andancillary parts to secure the propellers, all of which form an aligningsystem. The barrel fits into what becomes the trailing propeller whichis coupled and aligned to a leading propeller without adhesivelysecuring or welding. The leading propeller is any existing propeller.Thus, the coupling of the trailing propeller with the leading propelleris not time-consuming and less labor-intensive to combine than existingwelding or attaching techniques. The absence of welding eliminates apotential misalignment of the trailing propeller and the leadingpropeller. Further, the trailing propeller may be attached to an engineirrespective of the engine manufacturer. Moreover, the trailingpropeller and leading propeller do not counter-rotate with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention, which are believed to be novel,are set forth with particularity in the appended claims. Embodiments ofthe present invention will hereinafter be described in conjunction withthe appended drawings provided to illustrate and not to limit the scopeof the claims, wherein like designations denote like elements, and inwhich:

FIG. 1 shows an isometric view of a dual propeller assembly;

FIG. 2 shows an isometric view of a torsion bushing;

FIG. 3 shows an isometric view of a thrust washer;

FIG. 4A shows an isometric view of a leading propeller of the propellerassembly of FIG. 1;

FIG. 4B shows an isometric view of the leading propeller with thetorsion bushing and the thrust washer;

FIG. 5 shows an isometric view of a drive sleeve (or spline);

FIG. 6A shows an isometric view of a trailing propeller;

FIG. 6B shows a side view of the trailing propeller;

FIG. 6C shows a top view of the trailing propeller; and

FIG. 6D shows an isometric view of the trailing propeller holding thedrive sleeve.

FIG. 7 shows a lead propeller to receive a trailing propeller.

FIG. 8 shows a trailing propeller with a different pitch than shown inFIG. 7.

DETAILED DESCRIPTION OF THE EMBODIMENTS

As used in the specification and claims, the singular forms “a”, “an”and “the” include plural references, unless the context clearly dictatesotherwise. For example, the term “an article” may include a plurality ofarticles unless the context clearly dictates otherwise.

Those with ordinary skill in the art will appreciate that the elementsin the figures are illustrated for simplicity and clarity, and are notnecessarily drawn to scale. For example, the dimensions of some of theelements in the figures may be exaggerated, relative to other elements,in order to improve an understanding of the invention.

There may be additional components described in the foregoingapplication that are not depicted in any of the described drawings. Inthe event such a component is described, but not depicted in a drawing,the absence of such a drawing should not be considered an omission ofthe design from the specification.

Before describing the present invention in detail, it should be observedthat it utilizes a combination of system components, which constitutesan axial alignment of two propellers. Accordingly, the components andthe method steps have been represented, showing only specific detailsthat are pertinent for an understanding of the present invention, so asnot to obscure the disclosure with details that will be readily apparentto those with ordinary skill in the art, having the benefit of thedescription herein.

As required, detailed embodiments of the present invention are disclosedherein. However, it should be understood that the disclosed embodimentsare merely exemplary of the invention, which can be embodied in variousforms. Therefore, the specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as abasis for the claims and as a representative basis for teaching oneskilled in the art to variously employ the present invention invirtually any appropriately detailed structure. Further, the terms andphrases used herein are not intended to be limiting, but to provide anunderstandable description of the invention.

The present invention comprises a barrel having grooves and itsancillary parts. The barrel fits into a trailing propeller that issecured and aligned coaxially with a leading propeller to form a dualpropeller assembly. In its simplest form, the barrel fits into thetrailing propeller with its smooth end, and the grooves are secured intothe leading propeller. The propeller assembly facilitates the movementof a watercraft when the propeller shaft of the leading propeller, whichis connected to a driver shaft which is in turn connected to an engineof the watercraft, is rotated. For easy understanding, the forthcomingspecification first describes various components and assembly of theleading propeller. The assembly can be configured manually without needfor tools or welding. Then, the components and assembly of the trailingpropeller of the present invention are described, along with thecomplete propeller assembly of the leading propeller and the trailingpropeller. The leading propeller includes an assembly of a cylindricalhub and multiple blades. The trailing propeller includes first andsecond cylindrical hubs, a conical profile, and multiple blades.

Referring now to FIG. 1, a propeller assembly 100 that includes aconventional leading propeller 102 and a trailing propeller 104 of thepresent invention, in accordance with an embodiment of the presentinvention is shown. The leading propeller 102 includes three blades 106a, 106 b, and 106 c. The trailing propeller 104 includes three blades106 d, 106 e, and 106 f (106 f not shown). The trailing propeller 104 issecured and aligned coaxially with the leading propeller 102 to generatean increased thrust force especially useful for a boat in shallow water.A 3-blade prep is shown for exemplary purposes and any number ofsuitable blades may be used herein provided a coaxial alignment isachieved in the assembly.

FIG. 2 illustrates an isometric view of a torsion bushing 202 thatprotects the engine of the watercraft. The torsion bushing 202 has acylindrical body which is tapered along its length. The torsion bushing202 thus has different diameters at the two ends thereof. Further, thetorsion bushing 202 has multiple grooves on its inner surface. Thetorsion bushing 202 axially twists along the longitudinal axis in theevent of an impact, such as the collision of the watercraft with anobstacle. To facilitate such axial twisting the torsion bushing 202 ismade of a resilient material. An exemplary resilient material for thefabrication of the torsion bushing 202 is an elastomeric polymer, orheavy duty plastic (for example, polyethylene, polypropylene, ABS, andthe like) provided it can withstand sheer and temperature forces it willbe exposed to. It can also be made of suitable metals such as brass,stainless steel, cast iron, and the like. The torsion bushing can bemanufactured, or purchased from a suitable manufacturers such asEvinrude, Mercury, or Honda (or other motor engines manufacturers). Thepresent invention used a bushing from a Mercury engine.

FIG. 3 illustrates a thrust washer 302 (also referred to as washer) thatprevents movement along the axis of a shaft. The thrust washer 302 ispositioned towards the end of the propeller assembly 100 that isattached to the engine, to prevent damage to gears and other operatingparts (not shown) of the outboard/inboard motor. The washer has a smoothbeveled interior to allow for a secure fit of the components. The washercan be manufactured, or purchased from a suitable manufacturer. Thepresent invention used a washer from the manufacturer Mercury.

Mercury brand hubs or boat parts in general (in particular spline or hubsystem) are relatively universal and fit most to all boats, includingEvinrude brand boats. With perhaps slight adapting, Mercury brand partscan be made to work with all or most boat brands.

FIGS. 4A and 4B illustrate the leading propeller 102 of the propellerassembly 100. FIG. 4A illustrates the leading propeller 102 without thethrust washer 302. The leading propeller 102 includes a cylindrical hub402, a cylindrical mount 404, and radial flanges 406 a-406 c. The blades106 a-106 c extend from an outer surface of the cylindrical hub barrel402. One end of the cylindrical mount 404 has a diameter equal to thelarger diameter of the torsion bushing 202. The leading propeller 102can be made of either aluminum, stainless steel or other similarmaterials. Further, FIG. 4B illustrates the leading propeller 102 withthe thrust washer 302 attached at one end thereof. The thrust washer 302has an opening that receives the propeller shaft and is tightly fittedin the cylindrical mount 404. The thrust washer 302 has a conicalsurface at the bottom thereof, which allows it to rest on thecylindrical mount 404 and top of the end of torsion bushing 202, whichhas a smaller diameter.

FIG. 5 illustrates a drive sleeve 502 that has a cylindrical body 504, acircular flange 506 and a cylindrical head 508. The drive sleeve 502includes a first set of splines, two of which are shown in the FIGS.5-510 a and 510 b—that extend along the cylindrical body 504. Thecircular flange 506 is positioned between the cylindrical body 504 andthe cylindrical head 508. The cylindrical head 508 includes a second setof splines internally that assist the propeller shaft to pass throughthe drive sleeve 502. In one embodiment, the drive sleeve 502 is made ofbronze but can also be made of stainless steel, iron, aluminum,elastomeric polymer or the like, or other suitable material whichresults in a solid sleeve. Further, the length of the cylindrical body504 is more than that of a standard drive sleeve such that the trailingpropeller 104 can be easily coupled to the leading propeller 102. Eachgroove of the torsion bushing 202 is arranged to receive thecorresponding spline of the drive sleeve 502. The grooves are tapered toenable maximum torsional twisting and distribute stress evenly along thetorsion bushing 202 in the event of a significant impact. The drivesleeve can be manufactured, or purchased from a suitable manufacturersuch as Mercury. The present invention used a Mercury brand purchasedsleeve.

FIGS. 6A-6D illustrate the trailing propeller 104 of the dual propellerassembly 100 of FIG. 1. As shown in FIGS. 6A and 6B, the inventivebarrel 602 is installed inside the trailing propeller 104. FIG. 6Aincludes a first cylindrical hub 602, a second cylindrical hub 604, anda conical profile 606 there between. The diameter of the firstcylindrical hub 602 is less than that of the second cylindrical hub 604.The conical profile 606 is formed between the first cylindrical hub 602and the second cylindrical hub 604. One end of the first cylindrical hub602 includes multiple grooves 606, three of which are identified as 606a-606 c. The grooves 606 are equally spaced and are locked onto theradial flanges 406 a-406 c of the leading propeller 102 (see FIG. 4B).There may be more or less than three grooves on the first cylindricalhub 602, generally 3-12 grooves on hub 602, without departing from thescope and spirit of the present invention.

The torsion hub holds the trailing propeller in place with a locking nuton the engine shaft. (See FIG. 6D).

As shown in FIG. 6C, the trailing propeller 104 includes a cylindricalmount ring 608 with radial mount ring flanges 610 a-610 c. The radialmount ring flanges 610 a-610 c are attached to the internal surface ofthe second cylindrical hub 604 to affix the cylindrical mount ring 608to the trailing propeller 104. The blades 106 d-106 f extend from theouter surface of the second cylindrical hub 604. It will be wellunderstood to a person skilled in the art that the number of bladesattached to the trailing propeller 104 may vary. While blades impactthrust, blades are not the primary scope of the present invention.

Cylindrical hub 602 fits inside of hub 402 to serve as the alignmentsystem for the dual propeller assembly. The outer diameter of the hub602 is sized so as to secure to the cylindrical hub barrel 402 of theleading propeller 102. The diameter can be modified (reduced orexpanded) with a lathe to fit different propellers; or increased indiameter with rubber shims. For example in FIG. 6A, rubber shims may beplaced and heat shrunk over the slots to alter the diameter. When thetrailing propeller 104 is coupled to the leading propeller 102, themultiple grooves 606 a-606 c of the first cylindrical hub 602 are lockedon the corresponding radial flanges 406 a-406 c of the leading propeller102. The conical profile 606 allows the trailing propeller 104 to alignwith the tapered end of the leading propeller 102.

In one embodiment and as shown herein, the grooves 606 a-606 c arerectangular in shape and symmetrical to ensure that the trailingpropeller 104 is aligned comfortably with the leading propeller 102. Tosecure the trailing propeller 104 to the leading propeller 102, thedrive sleeve 502 is inserted through the cylindrical mount ring 608 ofthe trailing propeller 104 into the leading propeller 102. The circularflange 506 of the drive sleeve 502 rests on the cylindrical mount ring608. FIG. 6D illustrates that the trailing propeller 104 holds the drivesleeve 502. The torsion bushing 202 of the leading propeller 102receives the cylindrical body 504 of the drive sleeve 502. The design ofthe trailing propeller 104 makes it easy to mechanically align it withthe leading propeller 102. The alignment allows the leading and trailingpropellers 102 and 104 to work together in sync. The assembly works bestwhen the leading and trailing propellers are aligned.

The propeller shaft (not shown) has a tapered section for mating withthe thrust washer 302, and a splined section for mating with the drivesleeve 502. Further, the propeller shaft includes a threaded section toreceive the nut (not shown). To secure the propeller assembly 100 to thepropeller shaft, the torsion bushing 202 is inserted into thecylindrical hub barrel 402. Further, the trailing propeller 104 isaligned with the leading propeller 102 by means of the grooves 606 a-606c and the radial flanges 406 a-406 c. The drive sleeve 502 is insertedinto the leading propeller 102 through the torsion bushing 104. Thepropeller assembly 100 is then affixed to the propeller shaft such thatthe propeller shaft is inserted with the drive sleeve 502. A washer isthen affixed to the propeller shaft. Subsequently, the nut is placed onthe propeller shaft so that the washer is tightly secured to the drivesleeve 502. Thus, propeller assembly 100 is secured to the propellershaft.

When the propeller shaft rotates, the torque, generated as a result ofthe rotation, is transferred to the drive sleeve 502, and then to thetorsion bushing 202, followed by to the cylindrical hub barrel 402 ofthe leading propeller 102. Consequently, the torque is then transferredfrom the leading propeller 102 to the trailing propeller 104. Thepropeller assembly 100 is intact and ensures that the trailing propeller104 spins synchronously with the leading propeller 102.

The trailing propeller 104 may be manufactured using either of aninvestment casting method or a machining method. Further, the trailingpropeller 104 can be made of materials such as steel, aluminum,stainless steel, plastic, carbon fiber, all types of carbon, andfiberglass, the most preferred materials being stainless steel andaluminum. The first and second cylindrical hubs 602 and 604 of thetrailing propeller 104 can be made of heavy-duty plastic if desired.Plastics such as described above. In another embodiment, the first andsecond cylindrical hubs 602 and 604 of the trailing propeller 104 can bemade of aluminum.

The trailing propeller 104 can be constructed in all dimensions to fitleading propellers of 5 horsepower (hp) to 400 hp in size. The trailingpropeller 104 works using engines having a power range of about 115 hpto 400 hp. The propeller assembly 100 creates a stronger thrust forcethan a single propeller assembly. The use of the propeller assembly 100is recommended for water of less than 12 inches, and has been found tobe the most beneficial in extremely shallow water (of about or less than6″ deep) operations, as the propeller assembly provides a strong thrust.

For exemplary purposes, preferred dimensions of the trailing propeller104 are: the diameter (about 3″ to about 4.25″) and length (about 2.5″to about 4″) of the first cylindrical hub 602 are preferably about 4.16″and 3″, respectively. The diameter of the second cylindrical hub 604 isabout 3″-5″ and preferably about 4.81″. The length of the trailingpropeller 104 is about 7″-10″ with a preference for about 9-10 inches.The inner and outer diameters of the cylindrical mount ring 608 areabout 1″-1.75″ with a preference for about 1.65″ to about 1.75″ and2″-3″ with a preference for about 2.25 inches, respectively. Thethickness of the first cylindrical hub 602 is about 0.10″-0.250″ with apreference for a thickness of about 0.20″.

The leading and trailing propellers 102 and 104 align axially and spinsynchronously. This allows the propeller assembly 100 to maintaincontact with the water effectively and hold more water mass on theleading and trailing propellers 102 and 104. This improves the holeshot. Further, the propeller assembly 100 enhances steering and handlingof the watercraft. The trailing propeller 104 works with most if not alltypes of outboard and inboard motors. Moreover, the design of thetrailing propeller 104 adapts to most if not all marine enginesavailable. Experiments were conducted with a trailing propeller (104)having a standard V6 barrel. The dimensions of the trailing propeller104 can be adjusted to fit most if not all outboard propellers.

It was found that the propeller assembly 100, with the leading andtrailing propellers 102 and 104, retains water on the blades for twiceas long as under normal conditions. This allows the blades to remain incontact with water, even though half of the propeller assembly 100 isoutside of the water. The propeller assembly 100 allows outboards to getin very shallow water while doing the least amount of damage possible tothe environment. It was also found that the propeller assembly 100 canoperate completely above the running surface in a river with one-thirdto one-half of the blades on the water surface.

The alignment technique uses the geometry of the common outboardpropeller to align the trailing propeller 104 mechanically. The trailingpropeller 104 can be effectively and consistently used with propellersmade by other manufacturers and it is accomplished with no loss of speedto the engine. The additional cupping of the blades, changing from 3 to4 blades or 4 to 3 blades in the case of 4 stroke engines, enablesadditional rotations per minute (rpm) of the propeller assembly 100.

The barrel can be configured by adding slots and interior footing. Thebarrel may be modified to accept interchangeable blades allowinginterchangeable pitch. This occurs by switching out the different pitchblades. An embodiment of this interchangeable system is use of polymericcomposite materials, or aluminum, or stainless steel. The changing ofmaterials allows for a less costly assembly for customers without a lossof performance. The user can experiment with pitch size for their boat,and or a single blade replacement for the propeller assembly, anddetermine what works best while the boat is in the water.

Another alternate embodiment is having a bevel on the lead barrel whichallows a stop point for the trailing blades attached to the trailingbarrel. This creates an assembly.

Collectively, FIGS. 7 and 8 illustrate that the invention can bemodified for different boating needs of the user. This invention allowsfor modification of the pitch, blade and blade numbers, slots, andbarrel to accurately select a correct configuration for a boatingset-up. One of skill in the art will appreciate that the inventivepropeller assembly herein, will consider factors such as boat engine,size, and gear ratio to ultimately create stern lift for the boat. Thepitch of the blade can be varied, both front and rear, to accommodatedifferent boating applications of the user. As the pitch varies,generally the position of the blade on the barrel will vary.

Example

A turbo 1 Yamaha brand prop (the leading prop) was employed to alignwith the inventive trailing propeller. The trailing propeller slidesdirectly over the radial flanges of the leading propeller adjustingevenly so as alignment of the hubs is intact. The propeller assembly wasplaced on a 21 foot boat and taken to water having 6″ of depth to createa hole shot situation. It was found that the 21′ boat while standing in6″ of water was able to move out of the water in ½ of the boat length.

Comparative: The same boat was in the hole shot with the standard turbo1 Yamaha brand prop, and no trailing inventive propeller to form theassembly. The boat was not able to get on plane at all, or out of thewater, and needed to drive in circles to get itself out of the holeshot. When compared to a high performance engine (hole shot prop) thedistance to plane was 4 times as long in the above situation. In about12″ of water, this depth still considered shallow, the 21′ test boatrequired more than a boat length to get on plane and needed to drive incircles to get out of the hole.

The propeller assembly 100 solves a poor hole shot problem without lossof speed and wears out slowly because of its efficiency. Although allcupping can be removed by wearing out of a propeller, the inventivepropeller assembly 100 outperforms most of the modified propellers. Itwas seen that even though the propeller assembly 100 was completely wornout, it had a better hole shot than other modified propellers.Alternatively, when standard propellers exhibit little performance, ithas been found that the present invention does not allow performance tosuffer; both propellers can have significant wear and with the inventiveprop, still perform better than a new or refurbished (“mint condition”)standard propeller. The ability to couple the leading and trailingpropellers 102 and 104 together improves hole shot with minimal to zeroloss of speed. Further, the propeller assembly 100 design allows for thewearing out of the leading propeller 102 while protecting the wearingoff of the trailing propeller 104. This allows a user to upgrade theperformance of a propulsion system without replacing both thepropellers. The propeller assembly 100 allows a boat to move out ofshallow water in about a third to half the RPMS of its normal speed.

The leading propeller 102 and the trailing propeller 104 are coupled andaligned without welding. The propeller assembly 100 allows coupling ofthe leading and trailing propellers 102 and 104 in minimum time andeliminates potential misalignment from welding. The propeller assembly100 can be used with both 4-stroke and 2-stroke motors. The leading andtrailing propellers 102 and 104 do not counter-rotate.

While not wishing to be bound by theory, hole shot (thrust) is maximizedby allowing water to remain on more blade surface (generally twice asmany blades). The length of the propeller and number of blades maximizesthe working force at hole shot. As speed increases, the turbulence ofthe leading propeller negates the efficiency of the trailing propeller.As propeller speed increases boat speed, the trailing prop idles along,synchronous to the leading propeller. This allows boats to achievemaximum speeds while delivering superior hole shot. Hole shot isincreased between 60% to about 80% by adding, and correctly using, thepresent invention to an existing propeller.

It has been found that the present invention impacts steering of theboat and changes the steering from propeller driven to more jet-boatlike driven. The handling and steering change once the inventivepropeller assembly is installed and creates a safer operation, inparticular a reduced blow-out during turns resulting from propellerventilation often found on standard propeller systems. The reversethrust is enhanced with the inventive propeller assembly and results inease and improved stopping, especially important when the boat is nearor around decks or docks.

Table 1 outlines the water depth and boat length found to get on plane,also known as moving out of the depth noted of water with a boat havingthe inventive propeller assembly. This shows the invention is directedto water less than 12″ (inches) deep, or areas where the bottom of thewater area is soft mud or clay. The boat reached plane within 3-10seconds and usually between 3-5 seconds, and in some cases, almostinstantaneously. The examples for Table 1 were conducted with a 23 footShoal Water Cat Boat.

TABLE 1 Water depth out of hole shot  0″(soft mud) 1 boat length 4″(soft mud) 1 boat length  6″ (clay bottom) ½ boat length 12″ (claybottom) ½ boat length 14″(hard sand) difficult to get out of; generallya boater will stay away from this condition because the hard sanddestroys equipment. To get out often requires 180-360 degree spin of theboat and this is then not using the invention.

It has been found that the speed performance is not lost as theinventive propeller assembly wears. Often with traditional propellersspeed is impacted, and almost always reduced with use or wear and tearof the propellers. With the inventive assembly, when it was newly placedon the boat, the speed was about 58 miles per hour. It was found afterabout 200 hours of use, the speed with the inventive propeller assemblywas 57 miles per hour. Comparatively, a Bravo 1, 4-blade propeller afterabout 50 hours of similar use, was running at a reduced maximum speed by5-10 miles per hour.

The present invention can produce hole shot in 12″ and usually 6″ orless of water without a counter rotating propeller. It can bemechanically assembled without the need to weld or cast the unit, thefront and trailing propellers can be interchanged, and the unit can beretrofitted on a standard outboard motor.

The present invention has been described herein with reference to aparticular embodiment for a particular application. Although theselected embodiments have been illustrated and described in detail, itshould be understood that various substitutions and alterations arepossible. Those with ordinary skill in the art and access to the presentteachings may realize that additional various substitutions andalterations are also possible without departing from the spirit andscope of the present invention, and as defined by the following claims.

What is claimed is:
 1. A trailing propeller that is secured to a leadingpropeller, the trailing propeller comprising: a first cylindrical hubhaving a plurality of grooves on one end; a second cylindrical hubhaving a cylindrical mount ring, wherein the cylindrical mount ring isattached to the second cylindrical hub by a set of radial mount ringflanges; and a conical profile formed between the first cylindrical huband the second cylindrical hub, wherein the trailing propeller issecured and aligned coaxially to the leading propeller by way of theplurality of grooves, the conical profile, and the cylindrical mountring.
 2. The trailing propeller of claim 1, wherein the firstcylindrical hub is received in a hub of the leading propeller.
 3. Thetrailing propeller of claim 2, wherein an outer diameter of the firstcylindrical hub is selected based on an inner diameter of the hub of theleading propeller.
 4. The trailing propeller of claim 1, wherein theplurality of grooves are spaced equidistant from each other.
 5. Thetrailing propeller of claim 1, wherein the plurality of grooves rest ona corresponding plurality of radial flanges of the leading propeller. 6.The trailing propeller of claim 1, further comprising a plurality ofblades that extend from a surface of the second cylindrical hub.
 7. Thetrailing propeller of claim 1, wherein a drive sleeve is engaged withthe cylindrical mount ring of the trailing propeller and the leadingpropeller.
 8. The trailing propeller of claim 1, wherein a propellershaft secures the trailing propeller with the leading propeller.
 9. Thetrailing propeller of claim 1, wherein the trailing propeller ismanufactured using at least one of an investment casting method and amachining process.
 10. The trailing propeller of claim 1, wherein thetrailing propeller is made of at least one of steel, stainless steel,carbon fiber, fiberglass, elastomeric polymer and aluminum.
 11. Thetrailing propeller of claim 1 wherein the leading propeller and thetrailing propeller are interchangeable.
 12. The trailing propeller ofclaim 1 retrofitted on to a standard outboard boat motor.
 13. Thetrailing propeller of claim 12 wherein the boat is in used and a holeshot is produced in 12″ of water.
 14. The trailing propeller of claim 13wherein a hole shot is produced in 6″ of water.
 15. A method ofassembling the trailing propeller of claim 1 wherein the trailingpropeller is assembled without adhesively securing the first cylindricalhub, the second cylindrical and the resultant conical profile.
 16. Thetrailing propeller of claim 12 having a length of 7″-10″.
 17. Thetrailer propeller of claim 16 secured to a boat engine wherein the boatis standing in 0″ to 12″ of water.
 18. The trailing propeller of claim17 wherein the boat is moved out of the water in less than 1 boatlength.
 19. The trailing propeller of claim 18 wherein the boat is movedout of the water in less than 10 seconds of time.